Diversity receiving systems and diversity antennas are well known in the communications art. In general, diversity antenna systems are used to accommodate the RF signal fading and multi-path signal propagation anomalies that are common at VHF and UHF frequencies. Signal fading and multi-path signals can adversely effect reception of a radio frequency's signal and, by selectively choosing one of two or more spatially separated antennas that pick up a signal, fading and multi-path effects can be reduced. Multiple antennas are routinely used with cellular telephones and automobile radios.
Multiple antennas are now also used with wireless microphone systems, which include a remote, low-power portable transmitter, the signals of which are received and demodulated by a receiver. As a wireless microphone is moved about a room, multi-path signals can adversely affect the demodulated audio output from the receiver because multi-path signals will produce phase anomalies in the reception process that sound like popping noise or may even cause complete audio loss. Accordingly, diversity antenna systems are now employed in such wireless microphone systems to overcome the adverse effects of multi-path and signal fading.
At least one problem with a diversity antenna system is switching the appropriate antenna to the receiver in such a way so as to seamlessly couple the receiver to the proper antenna. Prior art systems exist for selecting one, or a combination of two or more antennas to be coupled to a radio receiver. Some of these prior art systems are disclosed in U.S. Pat. No. 5,777,693 to Kishigami, et al. for a “diversity receiving apparatus for a mobile unit;” U.S. Pat. No. 5,517,686 to Kennedy, et al. for a “diversity Receiver for FM Stereo Utilizing a Pilot Tone Multiple For Phase Alignment of Received Signals;” U.S. Pat. No. 5,548,836 to Taromaru for a “Diversity Receiver;” U.S. Pat. No. 5,465,411 to Koike for a “Diversity Receiver With Switching Noise Reduction;” U.S. Pat. No. 4,293,955 to Gehr, et al. for a “Diversity Reception System;” U.S. Pat. No. 5,742,896 to Bose, et al. for a “Diversity Reception With Selector Switching at Super Audible Rate;” U.S. Pat. No. 5,697,083 to Sano for a “Diversity Receiver;” and see U.S. Pat. No. 5,603,107 to Gottfried, et al. for a “Switching System For Diversity Antenna FM Receiver.”
When high fidelity audio reproduction is required in a small size package and at the lowest possible cost, prior art diversity antenna switching system are too complex, too large, or too expensive. Prior art low cost, switching systems also suffer from audio switch noise spikes that they produce in the receiver when they perform a hard instantaneous switch over from one antenna to another. A low cost, compact, method, and apparatus for selecting one or more antennas in such a way that audio fidelity reproduction is maximized would be an improvement over the prior art.